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A malfunction at BP's Whiting Refinery in Indiana caused oil to spill into Lake Michigan. Chicago Mayor Rahm Emanuel says the public deserves a full report about what happened and how the company plans to prevent another spill. (Published Thursday, Mar 27, 2014)

"There was a leak the other day, and they're calling it minor," Emanuel told reporters Wednesday. "I expect a full accounting to the public and the city of Chicago of the damage that was done, how much, what the cleanup efforts were, how comprehensive they have been and what actions the company will take to ensure this doesn't happen again."

Raw: Oil Spills Into Lake Michigan After Refinery Malfunction

BP spokesman Scott Dean said the disruption was discovered around 4:30 p.m. Monday. It resulted in the discharge of crude oil from the refinery's cooling water outfall into the cove between the waste water treatment plant and the steel mill.

In a statement released Wednesday, BP said a "vast majority of oil" that had been visible on the surface of the water and on the shoreline has been recovered and crews continue to monitor the area.

"BP and federal agencies are assessing the shoreline to determine what, if any, next steps are required in the response," the company said.

It's still not clear how much oil was spilled into the lake.

Emanuel said the public deserves to know what happened and how BP plans to prevent another spill.

"This is about making sure our residents have safe water," he said.

Shedd Aquarium's wildlife and water quality experts said they do not believe there will be long-term adverse effects on Lake Michigan wildlife from the spill.

"The late-blooming spring was on our side, with many native fishes still off-shore because of the prolonged ice cover."

In a joint statement, Sens. Mark Kirk and Dick Durbin said they are encouraged to hear the spill is contained but are "extremely concerned" about the possibility of a future spill after BP recently announced a plan to nearly double its processing of heavy crude oil at the refinery.

"We plan to hold BP accountable for this spill and will ask for a thorough report about the cause of this spill, the impact of the Whiting Refinery’s production increase on Lake Michigan, and what steps are being taken to prevent any future spill.”